【发布时间】：2011-07-07 03:29:46
【问题描述】：
有没有一种简单的方法来创建像官方市场应用程序中看到的可扩展/可折叠块？
Market 应用的屏幕截图，当您点击“更多”按钮时，描述部分会以动画形式展开：
我知道SlidingDrawer，但它似乎不适合这样的东西——它应该放在叠加层中，并且不支持半开状态。
更新：
这是我半途而废的解决方案。这是一个扩展LinearLayout 的自定义小部件。它有点工作，但不能很好地处理边缘情况，比如内容高度小于collapsedHeight 参数。我敢肯定，只要有足够的凝视、挖掘代码和试验这些怪癖，就可以解决。希望避免这样做，并通过使用现成的官方或第 3 方解决方案节省一些时间。无论如何，这里是，代码：
package com.example.androidapp.widgets;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.widget.LinearLayout;
import com.example.androidapp.R;
public class ExpandablePanel extends LinearLayout {
private final int mHandleId;
private final int mContentId;
private View mHandle;
private View mContent;
private boolean mExpanded = true;
private int mCollapsedHeight = 0;
private int mContentHeight = 0;
public ExpandablePanel(Context context) {
this(context, null);
}
public ExpandablePanel(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray a = context.obtainStyledAttributes(attrs,
R.styleable.ExpandablePanel, 0, 0);
// How high the content should be in "collapsed" state
mCollapsedHeight = (int) a.getDimension(
R.styleable.ExpandablePanel_collapsedHeight, 0.0f);
int handleId = a.getResourceId(R.styleable.ExpandablePanel_handle, 0);
if (handleId == 0) {
throw new IllegalArgumentException(
"The handle attribute is required and must refer "
+ "to a valid child.");
}
int contentId = a.getResourceId(R.styleable.ExpandablePanel_content, 0);
if (contentId == 0) {
throw new IllegalArgumentException(
"The content attribute is required and must refer "
+ "to a valid child.");
}
mHandleId = handleId;
mContentId = contentId;
a.recycle();
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
mHandle = findViewById(mHandleId);
if (mHandle == null) {
throw new IllegalArgumentException(
"The handle attribute is must refer to an"
+ " existing child.");
}
mContent = findViewById(mContentId);
if (mContent == null) {
throw new IllegalArgumentException(
"The content attribute is must refer to an"
+ " existing child.");
}
mHandle.setOnClickListener(new PanelToggler());
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
if (mContentHeight == 0) {
// First, measure how high content wants to be
mContent.measure(widthMeasureSpec, MeasureSpec.UNSPECIFIED);
mContentHeight = mContent.getMeasuredHeight();
}
// Then let the usual thing happen
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
private class PanelToggler implements OnClickListener {
public void onClick(View v) {
Animation a;
if (mExpanded) {
a = new ExpandAnimation(mContentHeight, mCollapsedHeight);
} else {
a = new ExpandAnimation(mCollapsedHeight, mContentHeight);
}
a.setDuration(500);
mContent.startAnimation(a);
mExpanded = !mExpanded;
}
}
private class ExpandAnimation extends Animation {
private final int mStartHeight;
private final int mDeltaHeight;
public ExpandAnimation(int startHeight, int endHeight) {
mStartHeight = startHeight;
mDeltaHeight = endHeight - startHeight;
}
@Override
protected void applyTransformation(float interpolatedTime,
Transformation t) {
android.view.ViewGroup.LayoutParams lp = mContent.getLayoutParams();
lp.height = (int) (mStartHeight + mDeltaHeight * interpolatedTime);
mContent.setLayoutParams(lp);
}
@Override
public boolean willChangeBounds() {
// TODO Auto-generated method stub
return true;
}
}
}
这里是res/values/attrs.xml：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="ExpandablePanel">
<attr name="handle" format="reference" />
<attr name="content" format="reference" />
<attr name="collapsedHeight" format="dimension" />
</declare-styleable>
</resources>
这是我在布局中使用它的方式：
<com.example.androidapp.widgets.ExpandablePanel
android:orientation="vertical"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
example:handle="@+id/expand"
example:content="@+id/value"
example:collapsedHeight="50dip">
<TextView
android:id="@id/value"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:maxHeight="50dip"
/>
<Button
android:id="@id/expand"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="More" />
</com.example.androidapp.widgets.ExpandablePanel>
【问题讨论】：
-
查看stackoverflow.com/questions/3695856/… - 接受的答案有一些可能感兴趣的第三方库。 code.google.com/p/android-misc-widgets/source/browse/trunk/… 特别是这个。